[automerger] Fix overflow/dos in 3gg text description parsing am: 851e22d1...

[automerger] Fix overflow/dos in 3gg text description parsing am: 851e22d1 am: efeff077 am: 93e7dd1e am: 0d6a0e7d am: ec9f664d am: 806e1cbf am: e44b6c78 am: 6ea9da93 am: c17a483a am: 34b9e0b6 am: 50a252f4
am: d219c012

Change-Id: Ie3902da59e7976f65df6aec7293e3f2cf030361a